1. Field of the Invention
The present invention relates to biodegradable polyesteramides Q1 with a molecular weight (M.sub.n) in the range from 5,000 to 50,000 g/mol, a viscosity number in the range from 30 to 450 g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polyesteramide Q1 at 25.degree. C.) and a melting point in the range from 50 to 220.degree. C., obtainable by reacting a mixture consisting essentially of
(a1) from 95 to 99.9% by weight of a polyesteramide P1 obtainable by reacting a mixture consisting essentially of
(b1) a mixture consisting essentially of
35-95 mol % of adipic acid or ester-forming derivatives thereof or mixtures thereof, PA1 5-65 mol % of terephthalic acid or ester-forming derivatives thereof or mixtures thereof, and PA1 0-5 mol % of a compound containing sulfonate groups, where the total of the individual mole percentages is 100 mol %, and PA1 (b21) 99.5-0.5 mol % of a dihydroxy compound selected from the group consisting of C.sub.2 -C.sub.6 -alkanediols and C.sub.5 -C.sub.10 -cycloalkanediols, PA1 (b22) 0.5-99.5 mol % of an amino-C.sub.2 -C.sub.12 -alkanol or of an amino-C.sub.5 -C.sub.10 -cycloalkanol, and PA1 (b23) 0-50 mol % of a diamino-C.sub.1 -C.sub.8 -alkane, PA1 (b24) 0-50 mol % of a 2,2'-bisoxazoline of the general formula I ##STR1## where R.sup.1 is a single bond, a (CH.sub.2).sub.q -alkylene group with q=2, 3 or 4, or a phenylene group, where the total of the individual mole percentages is 100 mol %, PA1 and where the molar ratio of (b1) to (b2) is chosen in the range from 0.4:1 to 1.5:1, PA1 with the proviso that the polyesteramides P1 have a molecular weight (M.sub.n) in the range from 4,000 to 40,000 g/mol, a viscosity number in the range from 30 to 450 g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polyesteramide P1 at 25.degree. C.) and a melting point in the range from 50 to 220.degree. C., and with the further proviso that from 0 to 5 mol %, based on the molar amount of component (a1) used, of a compound D with at least three groups capable of ester formation are used to prepare the polyesteramides P1, PA1 35-95, preferably from 45 to 80, mol % of adipic acid or ester-forming derivatives thereof, in particular the di-C.sub.1 -C.sub.6 -alkyl esters such as dimethyl, diethyl, dipropyl, dibutyl, dipentyl and dihexyl adipate, or mixtures thereof, preferably adipic acid and dimethyl adipate, or mixtures thereof, PA1 5-65, preferably 20-55, mol %, of terephthalic acid or ester-forming derivatives thereof, in particular the di-C.sub.1 -C.sub.6 -alkyl esters such as dimethyl, diethyl, dipropyl, dibutyl, dipentyl or dihexyl terephthalate, or mixtures thereof, preferably terephthalic acid and dimethyl terephthalate, or mixtures thereof, and PA1 0-5, preferably from 0 to 3, particularly preferably from 0.1 to 2, mol % of a compound containing sulfonate groups, PA1 where the total of the individual mole percentages is 100 mol %, and PA1 (b21) 99.5-0.5, preferably 99.5-50, particularly preferably 98.0-70, mol % of a dihydroxy compound selected from the group consisting of C.sub.2 -C.sub.6 -alkanediols and C.sub.5 -C.sub.10 -cycloalkanediols, PA1 (b22) 0.5-99.5, preferably 0.5-50, particularly preferably 1 to 30, mol % of an amino-C.sub.2 -C.sub.12 -alkanol or of an amino-C.sub.5 -C.sub.10 -cycloalkanol, and PA1 (b23) 0-50, preferably from 0 to 35, particularly preferably from 0.5 to 30, mol % of a diamino-C.sub.1 -C.sub.8 -alkane, PA1 (b24) 0-50, preferably 0-30, particularly preferably 0.5-20, of a 2,2'-bisoxazoline of the general formula I ##STR2## where R.sup.1 is a single bond, an ethylene, n-propylene or n-butylene group, or a phenylene group , and R.sup.1 is particularly preferably n-butylene, where the total of the individual mole percentages is 100 mol %, PA1 where the molar ratio of (b1) to (b2) is chosen in the range from 0.4:1 to 1.5:1, preferably from 0.6:1 to 1.1:1. PA1 where the amino carboxylic acid B1 is selected from the group consisting of the natural amino acids, polyamides with a molecular weight not exceeding 18,000 g/mol, preferably not exceeding 15,000 g/mol, obtainable by polycondensation of a dicarboxylic acid with 4 to 6 carbon atoms and a diamine with 4 to 10 carbon atoms and compounds which are defined by the formulae IIa or IIb ##STR3## where p is an integer from 1 to 1,500, preferably from 1 to 1,000, and r is 1, 2, 3 or 4, preferably 1 and 2, and G is a radical selected from the group consisting of phenylene, --(CH.sub.2).sub.n --, where n is an integer from 1 to 12, preferably 1, 5 or 12, --C(R.sup.2)H-- and --C(R.sup.2)HCH.sub.2, where R.sup.2 is methyl or ethyl, and polyoxazolines of the general formula III ##STR4## where R.sup.3 is hydrogen, C.sub.1 -C.sub.6 -alkyl, C.sub.5 -C.sub.8 -cycloalkyl, phenyl which is unsubstituted or substituted up to three times by C.sub.1 -C.sub.4 -alkyl groups, or tetrahydrofuryl, PA1 35-95, preferably from 45 to 80, particularly preferably from 45 to 70, mol % of adipic acid or ester-forming derivatives thereof or mixtures thereof, PA1 5-65, preferably from 20 to 55, particularly preferably from 30 to 55, mol % of terephthalic acid or ester-forming derivatives thereof or mixtures thereof, and PA1 0-5, preferably from 0 to 3, particularly preferably from 0.1 to 2, mol % of a compound containing sulfonate groups,
(b2) a mixture consisting essentially of
(a2) from 0.1 to 5% by weight of a divinyl ether C1 and
(a3) from 0 to 5 mol %, based on component (b1) from the preparation of P1, of compound D.
The invention furthermore relates to polymers and biodegradable thermoplastic molding compositions as claimed in the dependent claims, processes for the preparation thereof, the use thereof for producing biodegradable moldings and adhesives, biodegradable moldings, foams and blends with starch, obtainable from the polymers and molding compositions according to the invention.
2. Description of Related Art
Polymers which are biodegradable, ie. decompose under environmental influences in an appropriate and demonstrable time span, have been known for some time. This degradation usually takes place by hydrolysis and/or oxidation, but predominantly by the action of microorganisms such as bacteria, yeasts, fungi and algae. Y. Tokiwa and T. Suzuki (Nature, 270, (1977) 76-78) describe the enzymatic degradation of aliphatic polyesters, for example including polyesters based on succinic acid and aliphatic diols.
EP-A 565,235 describes aliphatic copolyesters containing [--NH--C(O)O--] groups (urethane units). The copolyesters of EP-A 565,235 are obtained by reacting a prepolyester, which is obtained by reacting essentially succinic acid and an aliphatic diol, with a diisocyanate, preferably hexamethylene diisocyanate. The reaction with the diisocyanate is necessary according to EP-A 565,235 because the polycondensation alone results only in polymers with molecular weights such that they display unsatisfactory mechanical properties. A crucial disadvantage is the use of succinic acid or ester derivatives thereof to prepare the copolyesters because succinic acid and derivatives thereof are costly and are not available in adequate quantity on the market. In addition, the polyesters prepared using succinic acid as the only acid component are degraded only extremely slowly.
Chain extension can, according to EP-A 534 295, also be advantageously achieved by reaction with divinyl ethers.
WO 92/13019 discloses copolyesters based on predominantly aromatic dicarboxylic acids and aliphatic diols, where at least 85 mol % of the polyester diol residue comprises a terephthalic acid residue. The hydrophilicity of the copolyester can be increased and the crystallinity can be reduced by modifications such as incorporation of up to 2.5 mol % of metal salts of 5-sulfoisophthalic acid or short-chain ether diol segments such as diethylene glycol. This is said in WO 92/13019 to make the copolyesters biodegradable. However, a disadvantage of these copolyesters is that biodegradation by microorganisms was not demonstrated, on the contrary only the behavior towards hydrolysis in boiling water or, in some cases, also with water at 60.degree. C. was carried out.
According to Y. Tokiwa and T. Suzuki, (Nature, 270 (1977), and J. Appl. Polymer Science, 26 (1981), 441-448), it can be assumed that polyesters built up substantially from aromatic dicarboxylic acid units and aliphatic diols, such as PET (polyethylene terephthalate) and PBT (polybutylene terephthalate), cannot be degraded enzymatically. This also applies to copolyesters containing blocks built up from aromatic dicarboxylic acid units and aliphatic diols.
In addition, Y. Tokiwa, T. Suzuki and T. Ando (J. of Appl. Polym. Sci. 24 (1979) 1701-1711) prepared polyesteramides and blends of polycaprolactone and various aliphatic polyamides such as polyamide-6, polyamide-66, polyamide-11, polyamide-12 and polyamide-69 by melt condensation and investigated their biodegradability by lipases. It was found that the biodegradability of such polyesteramides depends greatly on whether there is a predominantly random distribution of the amide segments or, for example, a block structure. In general, amide segments tend to reduce the rate of biodegradation by lipases.
However, the crucial factor is that no lengthy amide blocks are present, because it is known from Plant Cell Physiol. 7 (1966) 93, J. Biochem. 59 (1966) 537 and Agric. Biol. Chem. 39 (1975) 1219 that the usual alipatic and aromatic polyamides are biodegradable at the most only when oligomers, otherwise not.
Witt et al. (handout for a poster at the International Workshop of the Royal Institute of Technology, Stockholm, Sweden, Apr. 21-23, 1994) describe biodegradable copolyesters based on 1,3-propanediol, terephthalic ester and adipic or sebacic acid. A disadvantage of these copolyesters is that moldings produced therefrom, especially sheets, have inadequate mechanical properties.